Wire for deep water transmission

ABSTRACT

An electrically conductive wire for deep water transmission includes a first wire portion and a second wire portion. The first wire portion makes up one end of the wire, and is formed from a first metal. The second wire portion is formed from a second metal. The first metal has a higher ultimate tensile strength than the second metal. The first wire portion is used to support the weight of the second wire portion, thereby allowing the electrically conductive wire to be used in underwater or subsea power cables which may be freely suspended from their origin for providing electricity to electrical devices located in deep water or ultra-deep water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/040,272, filed Aug. 21, 2014, the entirety of which arefully incorporated by reference herein.

BACKGROUND

The present disclosure relates to electrically conductive wires. Theelectrically conductive wires are particularly useful for long powercables, such as those used to provide electricity to deep water devices.

Subsea oil and gas wells may be located in ultra-deep water devices(depths of 1500 meters or greater, ˜5000 feet). Providing electricity tosubsea devices at this depth requires suspending very long power cablesfrom a surface location at sea to a terminal location on the sea floor.The weight of these power cables is largely borne at the end of thepower cable secured to the surface location. The power cables are alsoaffixed to riser tubing/scaffolding coming up from the sea floor to bearthe weight of the cable. The need for such scaffolding can complicatethe construction of the oil/gas well. In addition, the power cable willexperience large tensile forces and dynamic motion during its servicelifetime, for example due to movement of waves and/or ocean currents.The cable can also be exposed to torsional forces that twist the cable.

Power cables include metallic conductor wires, typically consisting ofcopper. These copper conductor wires generally have poor mechanicalproperties. In particular, the end of the conductor wire is usually notstrong enough to support the weight of the remaining wire in such longpower cables, resulting in failure due to various stress-relatedphenomena over time.

It would be desirable to develop new electrically conductive wires thathave improved mechanical strength as well as other desirable properties.

BRIEF DESCRIPTION

The present disclosure relates to electrically conductive wires that aresuitable for use in long subsea power cables. The wire is made of afirst wire portion and a second wire portion. The first wire portion islocated at one end of the wire, and is made of a metal that has a higherultimate tensile strength than the second wire portion. It iscontemplated that the first wire portion, i.e. the end of the wire, islocated at the end of the power cable that is secured to the surfacelocation, or in other words at the end that supports the weight of therest of the wire. This can reduce or eliminate the need for scaffoldingto support the weight of the power cable. In more specific embodiments,the second wire portion also has a higher electrical conductivity thanthe first wire portion.

Disclosed in various embodiments herein are electrically conductivewires for deep water transmission, having a first wire portion and asecond wire portion welded together; wherein the first wire portion isformed of a first metal, is located at one end of the wire, and has alength of about 100 feet or greater; wherein the second wire portion isformed of a second metal; and wherein the first metal has a higherultimate tensile strength than the second metal.

The first metal may have an ultimate tensile strength of 100 ksi orhigher. The first metal can be a copper-nickel-beryllium alloy. Morespecifically, the first metal may contain from about 0.2 wt % to about0.6 wt % of beryllium, about 1.4 wt % to about 2.2 wt % of nickel, andbalance copper.

The second metal may have an ultimate tensile strength of 75 ksi orless. The second metal may be at least 99.9 wt % copper.

In some embodiments, the second metal has a higher electricalconductivity than the first metal. In specific embodiments, the secondmetal has an electrical conductivity of 100% IACS or higher, and thefirst metal has an electrical conductivity of 80% IACS or lower.

The length of the first wire portion is less than the length of thesecond wire portion. In particular embodiments, the ratio of the lengthof the second wire portion to the ratio of the length of the first wireportion is from about 10:1 to about 50:1. More specifically, the lengthof the first wire portion can be from about 100 feet to about 500 feet,and the length of the electrically conductive wire can be about 2,000feet or longer.

The electrically conductive wire may have a diameter of from about 1millimeter to about 3 millimeters.

The electrically conductive wire may further comprise a third wireportion located at the other end of the wire which is formed of thefirst metal, is welded to the second wire portion, and has a length ofabout 100 feet or greater.

Also disclosed herein are power cables for deep water transmissioncomprising at least one core; and externally from the core: awater-proofing layer; an armor layer; and an external polymeric sheath.Each core comprises: an electrically conductive wire having a first wireportion and a second wire portion welded together, wherein the firstwire portion is formed of a first metal, is located at one end of thewire, and has a length of about 100 feet or greater, wherein the secondwire portion is formed of a second metal, and wherein the first metalhas a higher ultimate tensile strength than the second metal; an innersemiconductive layer; an electrically insulating layer; and an outersemiconductive layer.

In specific embodiments, the power cable has one to three cores.

Also disclosed are methods of providing power to a deep water devicecomprising: connecting a first end of a power cable to an above-waterpower source; and connecting a second end of the power cable to the deepwater device; wherein the power cable comprises an electricallyconductive wire having a first wire portion and a second wire portionwelded together, wherein the first wire portion is formed of a firstmetal, is located at one end of the wire, and has a length of about 100feet or greater, wherein the second wire portion is formed of a secondmetal, and wherein the first metal has a higher ultimate tensilestrength than the second metal; and wherein the first wire portion islocated at the first end of the power cable.

The deep sea device may rest on a sea floor and is a well fluidprocessing device. In some embodiments, the power source is on aplatform or a floating production, storage, and offloading (FPSO) unit.

These and other non-limiting characteristics of the disclosure are moreparticularly disclosed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which arepresented for the purposes of illustrating the exemplary embodimentsdisclosed herein and not for the purposes of limiting the same.

FIG. 1 is an exploded perspective view of a power cable having a singleconductor core.

FIG. 2 is a cross-sectional view of a power cable having three conductorcores.

FIG. 3 is a schematic view of a system for providing electricity to anunderwater device.

FIG. 4 is a cross-sectional schematic of an electrically conductive wireof the present disclosure.

FIG. 5 is a graph showing the electrical conductivity of a copper alloysuitable for use as the first metal at the end of the wire. Theconductivity is shown as a function of temperature (° F.). The specificvalues are provided in (deg° F., specific conductivity), and are (75,188); (125, 176); (250, 160); (300, 146); (450, 125); and (600, 112).

FIG. 6 is a graph showing the fatigue curve of a copper alloy suitablefor use as the first metal at the end of the wire. This shows themagnitude of a cyclic stress versus the number of cycles to failure. Thespecific values are provided in (cycles, MPa), and are (10⁶, 475); (10⁷,350); (10⁸, 325); (10⁹, 300); and (10¹⁰, 270).

DETAILED DESCRIPTION

A more complete understanding of the components, processes andapparatuses disclosed herein can be obtained by reference to theaccompanying drawings. These figures are merely schematicrepresentations based on convenience and the ease of demonstrating thepresent disclosure, and are, therefore, not intended to indicaterelative size and dimensions of the devices or components thereof and/orto define or limit the scope of the exemplary embodiments.

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the embodiments selected for illustration in thedrawings, and are not intended to define or limit the scope of thedisclosure. In the drawings and the following description below, it isto be understood that like numeric designations refer to components oflike function.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

As used in the specification and in the claims, the term “comprising”may include the embodiments “consisting of” and “consisting essentiallyof.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,”“contain(s),” and variants thereof, as used herein, are intended to beopen-ended transitional phrases, terms, or words that require thepresence of the named ingredients/steps and permit the presence of otheringredients/steps. However, such description should be construed as alsodescribing compositions or processes as “consisting of” and “consistingessentially of” the enumerated ingredients/steps, which allows thepresence of only the named ingredients/steps, along with any impuritiesthat might result therefrom, and excludes other ingredients/steps.

Numerical values in the specification and claims of this applicationshould be understood to include numerical values which are the same whenreduced to the same number of significant figures and numerical valueswhich differ from the stated value by less than the experimental errorof conventional measurement technique of the type described in thepresent application to determine the value.

All ranges disclosed herein are inclusive of the recited endpoint andindependently combinable (for example, the range of “from 2 grams to 10grams” is inclusive of the endpoints, 2 grams and 10 grams, and all theintermediate values).

A value modified by a term or terms, such as “about” and“substantially,” may not be limited to the precise value specified. Themodifier “about” should also be considered as disclosing the rangedefined by the absolute values of the two endpoints. For example, theexpression “from about 2 to about 4” also discloses the range “from 2 to4.”

As used in the specification and claims, the term “metal” refers to arelatively pure elemental metal (i.e., a metal containing a singleelement and impurities) or an alloy of two or more elements.

The present disclosure relates to electrically conductive wires, powercables containing the electrically conductive wires, and methods forproviding electricity to deep water devices using the power cables. Inthis regard, power cables may have one or more conductive cores.

FIG. 1 is a perspective view of a single-core power cable 1 contemplatedby the present disclosure, made up of several layers wrappedconcentrically about the core. The power cable 1 includes a conductor 2which is made up of a plurality of electrically conductive wires of thepresent disclosure. It is noted that the electrically conductive wirescan be straight or be helically wound. An inner semiconductive layer 3surrounds the core 2. Any gaps between the wires can be filled with awater-blocking compound. The next layers of the power cable are anelectrically insulating layer 4 and an outer semiconductive layer 5.Next, a water-proofing layer 6 provides an impermeable barrier from theexternal environment. An armor layer 7 is then present, which istypically made of one or two layers of helically wound wires. Finally, apolymeric sheath 8 encases the other layers. In a single-core cable, thepolymeric sheath 8 also forms the outer layer of the cable.

FIG. 2 is a perspective view of a three-core power cable 10 contemplatedby the present disclosure. The power cable includes three cores 15. Eachcore includes a conductor 2 made up of a plurality of electricallyconductive wires. Each core is also concentrically surrounded by aninner semiconductive layer 3, an electrically insulating layer 4, anouter semiconductive layer 5, a water-proofing layer 6, a metal screen12, and a polymeric sheath 8. These three separate cores 15 are thenbundled together with binder tape 20 concentrically surrounding thethree cores 15. A fiber-optic cable 25 can also be included in thebundle, if desired. Filler 24 can be used to fill any remaining spacewithin the binder tape layer 20. Another water-proofing or sheath layer26 can be placed around the binder tape 20. An armor layer 28 surroundsthe water-proofing layer 26 (only one layer of wires depicted), and anexternal polymeric sheath 30 encases the other layers and forms theouter layer of the three-core power cable.

The semiconductive layers 3, 5 may be made from the same or differentcompositions. The semiconductive layers are generally formed from thecombination of a polymer and a conductive filler. Non-limiting examplesof conductive fillers include carbon black, graphite, carbon nanotubes,doped inorganic carbon fillers (e.g., aluminum-doped zinc oxide),powders of intrinsically-conductive polymers, or a mixture thereof.

The electrically-insulating layer 4 can be any suitable polymer, forexample crosslinked polyethylene, ethylene-propylene rubber (EPR), orpolyvinyl chloride (PVC). The armor layer 7, 28 is typically formed fromtwo layers of contra-helically wound wire. The polymeric sheath 8, 26,30 can be formed from any suitable polymer, for example polyethylene.The metal screen 12 can be copper, aluminum, or steel. These aspects aregenerally known in the art.

FIG. 3 is a schematic view illustrating the use of a power cable 101 ofthe present disclosure to provide electricity to a deep sea device 130.One end of the power cable 101 is secured to a power source 110 at thesurface 112 of a body of water. The power source 110 may be a platformor a floating production, storage, and offloading (FPSO) unit. The otherend of the power cable 101 is connected to a deep sea device 130 restingon the sea floor 132. The power cable 101 is optionally supported by oneor more buoys 120. In the depicted embodiment, the deep sea device 130is a piece of well fluid processing and/or reinjection equipment. Theequipment 130 is located in a pathway 140 for extracting hydrocarbons(e.g., oil and/or gas) from a well beneath the sea floor 132. Theequipment 130 may be used to make improvements to production fluidsemanating from the well. For example, the equipment may safely separateunwanted solids, waters, or hydrocarbon phases prior to sending thedesired products to the surface. Such improvements may save costs andreduce risks of harm to people and the environment. The power cable ispreferably not supported by any scaffolding, and can be described asbeing freely suspended.

FIG. 4 is a schematic diagram of an electrically conductive wire 200according to the present disclosure, and is not drawn to scale. The wireincludes a first wire portion 210, a second wire portion 220, andoptionally a third wire portion 230. The first wire portion is locatedat one end 202 of the wire, and the third wire portion is located at theother end 204 of the wire, and they are generally identical when thethird wire portion is present. Put another way, the second wire portion220 is located between the first wire portion 210 and the third wireportion 230. The first wire portion 210 and the second wire portion 220are metallurgically connected at a joint 207 (e.g., a welded joint), andthe third wire portion 230 and the second wire portion 220 aremetallurgically connected at another joint 209. The electricallyconductive wire has a diameter 205 of from about 1 millimeter to about 3millimeters.

Again, one prior problem is that most of the weight of the electricallyconductive wire is borne by the end of the wire (and cable) that issecured to the power source at the surface. In the present disclosure,the first wire portion 210 and/or third wire portion are intended tocorrespond to the end of the wire that bears the weight of the wire,which mostly consists of the second wire portion 220. This is done byusing a first metal for the first wire portion and/or the third wireportion, and by using a second metal for the second wire portion. Thefirst metal has a higher ultimate tensile strength than the secondmetal. It is contemplated that the first metal and second metal bothcontain copper.

The first wire portion 210 has a minimum length 215 of about 100 feet orgreater. Keeping in mind that the length of the wire (and the powercable) are intended to reach to depths of 5000 feet or greater, thelength of the first wire portion can also be greater if desired. Thelength of the first wire portion can be about 500 feet, or about 1000feet, or about 2000 feet, or from about one hundred (100) feet to abouttwo thousand (2,000) feet. The length 215 of the first wire portion isless than the length 225 of the second wire portion. More specifically,the second wire portion is at least 50% of the length of the overallwire, and is usually much higher. In particular embodiments, the ratioof the length of the second wire portion to the ratio of the length ofthe first wire portion can be from about 5:1 to about 50:1, or fromabout 10:1 to about 20:1. In particular embodiments, the length of thefirst wire portion is from about 100 feet to about 500 feet, and thelength of the electrically conductive wire is about 2,000 feet orlonger.

A first metal is used to form the first wire portion and/or the thirdwire portion. In particular embodiments, the first metal is acopper-nickel-beryllium alloy. The copper-nickel-beryllium alloy maycontain from about 0.1 weight percent (wt %) to about 1 wt % beryllium.In some embodiments, the beryllium content is from about 0.2 to about0.6 weight percent. The copper-nickel-beryllium alloy may contain fromabout 1 wt % to about 3 wt % nickel. In some embodiments, the nickelcontent is from about 1.4 wt % to about 2.2 wt % nickel. In specificembodiments, the first metal contains from about 0.2 wt % to about 0.6wt % of beryllium, about 1.4 wt % to about 2.2 wt % of nickel, andbalance copper.

The copper-nickel-beryllium alloy may be Alloy 3 UNS Number C17510(commercially available from Materion Corporation). C17510 contains fromabout 0.2 wt % to about 0.6 wt % beryllium, from about 1.4 wt % to about2.2 wt % nickel, and a balance of copper. The Table below lists selectedphysical properties of C17510.

Selected Properties of C17510 Elastic Modulus 20 × 10⁶ psi (138 GPa)Density 0.319 lb/in³ (8.83 g/cm³) Poisson's Ratio  0.3 Relative MagneticPermeability <1.01 Electrical Conductivity 45-60% IACS (26.2-34.9 MS/m)Thermal Conductivity at 140 BTU/ft-hr-° F. (240 W/m-K) 70° F./20° C.Coefficient of Thermal Expansion 9.8 ppm/° F. (17.6 ppm/° C.) SpecificHeat (Heat Capacity) at 0.08 BTU/lb-° F. (335 J/kg K) 70° F./20° C.Specific Heat (Heat Capacity) at 0.091 BTU/lb-° F. (381 J/kg K) 200°F./100° C. Melting Range 1,900-1,980° F. (1,040-1,080° C.)

The first metal has an ultimate tensile strength of 100 ksi or higher.The copper-nickel-beryllium alloy may be age hardened to obtain suchproperties. Age hardening is a heat treatment of the alloy, and is acontrolled process of heating and cooling metals to alter the physicaland mechanical properties without changing the product shape. Heattreatment is associated with increasing the strength of the material butit can also be used to alter certain manufacturability objectives suchas to improve machining, improve formability, or to restore ductilityafter a cold working operation. The alloy is placed in a traditionalfurnace or other similar assembly and then exposed to an elevatedtemperature in the range of about 900° F. to about 950° F. for a timeperiod of from about 2 hours to about 3 hours. It is noted that thesetemperatures refer to the temperature of the atmosphere to which thealloy is exposed, or to which the furnace is set; the alloy itself doesnot necessarily reach these temperatures.

After age hardening, the copper-nickel-beryllium alloy may have a 0.2%offset yield strength of about 80 ksi to about 125 ksi, and may have anultimate tensile strength of about 100 ksi to about 140 ksi.

The second metal is used to form the second wire portion. The secondmetal may be relatively pure copper, and in particular embodimentscontains a minimum of 99.9 wt % copper. The second metal may beoxygen-free copper or electrolytic tough pitch copper. Generally,oxygen-free copper has better drawing and resistance to hydrogenembrittlement compared to electrolytic tough pitch copper, because itcontains less dissolved oxygen. The remainder of the second metal maybe, for example, silver, nickel, and/or tin, or other impurities.

In some embodiments, the second metal is C102 copper alloy. The C102 mayhave the properties listed in the Table below.

Selected Properties of C102 Electrical Conductivity 101% IACS @ 68° F.Electrical Resistivity 1.71 microΩ-cm @ 68° F. Melting Point 1981° F.Density 0.323 lbs/in³ (8.92 g/cm³) Coefficient of Thermal Expansion 9.8ppm/° F.

C102 copper alloy has a 0.2% offset yield strength of about 45 ksi toabout 60 ksi, and has an ultimate tensile strength of about 25 ksi toabout 75 ksi. In embodiments, the second metal has an ultimate tensilestrength of 75 ksi or less.

In some embodiments, the second metal is C110 copper alloy. The C110 mayhave the properties listed in the Table below.

Selected Properties of C110 Density 0.322 lb/in³ @ 68° F. (8.92 g/cm³)Thermal Conductivity 390 W/m-K Electrical Resistivity 1.71 microΩ-cmElectrical Conductivity (annealed) 101% IACS (0.586 megamho/cm) Modulusof Elasticity 17,000,000 psi (117 kN/mm²) Coefficient of ThermalExpansion 9.8 ppm/° F. (17.64 ppm/° C.)

C110 copper alloy has a 0.2% offset yield strength of about 45 ksi toabout 60 ksi, and has an ultimate tensile strength of about 25 ksi toabout 75 ksi.

In particular embodiments, the electrical conductivity of the secondwire portion is higher than the electrical conductivity of the firstwire portion. More specifically, the second metal may have an electricalconductivity of 100% IACS or higher, and the first metal may have anelectrical conductivity of 80% IACS or lower. The IACS refers to theInternational Annealed Copper Standard. 100% IACS is a conductivity of58,001,000 Siemens/meter (S/m) at 20° C.

The first wire portion, the second wire portion, and the third wireportion may be metallurgically connected via welding. After thedifferent wire portions/segments are welded together, they can be rolledand drawn to size as though they are one wire.

FIG. 5 is a graph showing the specific electrical conductivity ofage-hardened C17510 (the first metal used in the first wire portion).The y-axis is in units of % IACS-in³/lb, and the x-axis is in degreesFahrenheit. As seen here, the specific electrical conductivity increasesas the temperature decreases. It is noted that the temperature of thefirst wire portion will be higher than the temperature of the water inwhich the cable is immersed, due to functional resistance heating.Please note that these values need to be multiplied by the density toobtain the electrical conductivity.

FIG. 6 is a fatigue curve at room temperature for the age-hardenedC17510 (the first metal used in the first wire portion). This graph canbe interpreted as providing the number of cycles to failure for a givenapplied stress.

It will be appreciated that variants of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be combined intomany other different systems or applications. Various presentlyunforeseen or unanticipated alternatives, modifications, variations orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompassed by the following claims.

The invention claimed is:
 1. An electrically conductive wire for deepwater transmission having a first wire portion and a second wire portionwelded together; wherein the first wire portion is formed of a firstmetal, is located at one end of the wire, and has a length of about 100feet or greater; wherein the second wire portion is formed of a secondmetal; and wherein the first metal has a higher ultimate tensilestrength than the second metal; and wherein the length of the first wireportion is less than the length of the second wire portion.
 2. Theelectrically conductive wire of claim 1, wherein the first metal has anultimate tensile strength of 100 ksi or higher.
 3. The electricallyconductive wire of claim 1, wherein the first metal is acopper-nickel-beryllium alloy.
 4. The electrically conductive wire ofclaim 3, wherein the first metal contains from about 0.2 wt % to about0.6 wt % of beryllium, about 1.4 wt % to about 2.2 wt % of nickel, andbalance copper.
 5. The electrically conductive wire of claim 1, whereinthe second metal has an ultimate tensile strength of 75 ksi or less. 6.The electrically conductive wire of claim 1, wherein the second metal isat least 99.9 wt % copper.
 7. The electrically conductive wire of claim1, wherein the second metal has a higher electrical conductivity thanthe first metal.
 8. The electrically conductive wire of claim 1, whereinthe second metal has an electrical conductivity of 100% IACS or higher,and the first metal has an electrical conductivity of 80% IACS or lower.9. The electrically conductive wire of claim 1, wherein the ratio of thelength of the second wire portion to the ratio of the length of thefirst wire portion is from about 10:1 to about 50:1.
 10. Theelectrically conductive wire of claim 1, wherein the length of the firstwire portion is from about 100 feet to about 500 feet, and the length ofthe electrically conductive wire is about 2,000 feet or longer.
 11. Theelectrically conductive wire of claim 1, having a diameter of from about1 millimeter to about 3 millimeters.
 12. The electrically conductivewire of claim 1, further comprising a third wire portion located at theother end of the wire which is formed of the first metal, is welded tothe second wire portion, and has a length of about 100 feet or greater.13. A power cable for deep water transmission comprising: at least onecore, each core comprising: an electrically conductive wire having afirst wire portion and a second wire portion welded together, whereinthe first wire portion is formed of a first metal, is located at one endof the wire, and has a length of about 100 feet or greater, wherein thesecond wire portion is formed of a second metal, and wherein the firstmetal has a higher ultimate tensile strength than the second metal, andwherein the length of the first wire portion is less than the length ofthe second wire portion; an inner semiconductive layer; an electricallyinsulating layer; and an outer semiconductive layer; and externally fromthe core: a water-proofing layer; an armor layer; and an externalpolymeric sheath.
 14. The power cable of claim 13, wherein the powercable has three cores.
 15. The power cable of claim 13, wherein thefirst metal has an ultimate tensile strength of 100 ksi or higher, andwherein the second metal has an ultimate tensile strength of 65 ksi orlower.
 16. The power cable of claim 13, wherein the first metal is acopper-nickel-beryllium alloy containing from about 0.2 wt % to about0.6 wt % of beryllium, about 1.4 wt % to about 2.2 wt % of nickel, andbalance copper.
 17. The power cable of claim 13, wherein the secondmetal is at least 99.9 wt % copper.
 18. The power cable of claim 13,wherein the second metal has an electrical conductivity of 100% IACS orhigher, and the first metal has an electrical conductivity of 80% IACSor lower.
 19. A method of providing power to a deep water devicecomprising: connecting a first end of a power cable to an above-waterpower source; and connecting a second end of the power cable to the deepwater device; wherein the power cable has a conductor that comprises anelectrically conductive wire having a first wire portion and a secondwire portion welded together, wherein the first wire portion is formedof a first metal, is located at one end of the wire, and has a length ofabout 100 feet or greater, wherein the second wire portion is formed ofa second metal, and wherein the first metal has a higher ultimatetensile strength than the second metal; and wherein the first wireportion is located at the first end of the power cable.